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National Geologic Map Database

Geologic Unit: Northwestern

Usage:

Northwestern Formation (SD*)


Geologic age:

Paleoproterozoic*


Type section, locality, area and/or origin of name:

Named from exposures in cuts of Chicago and Northwestern RR between Lead and Blacktail, [Homestake Mine area, Lead district], Lawrence Co., southwestern SD (Hosted and Wright, 1923).


AAPG geologic province:

Midcontinent region*


For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.

Asterisk (*) indicates published by U.S. Geological Survey authors.

"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).

Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).